Reduced Vernier acuity, impaired cortical visual function found in Down syndrome

Invest Ophthalmol Vis Sci. 2009;50(2):567-572.

Issue: April 25, 2009

Reduced Vernier thresholds indicated impaired cortical visual function in children with Down syndrome. The study was the first to investigate Vernier performance and its impact on higher visual function in children with the condition.

"Down syndrome is associated with reduced visual performance," the study authors said. "Although poor optical quality has been implicated, no previous data are available regarding the contribution of cortical visual processes."

The study included 29 children ages 9 years to 16 years with Down syndrome. A control group comprised 68 age-matched developmentally normal children. Twenty-five Down syndrome subjects (86%) and 65 control subjects (96%) successfully completed Vernier testing. Mean Vernier acuity was 39.8 arc seconds in the Down syndrome group and 14.6 arc seconds in the control group. Data showed no significant correlations between age and Vernier acuity.

Further study may enable researchers to mitigate poor visual function in people with Down syndrome, the authors said.

"If it were possible to clinically intervene during the critical period in [Down syndrome], it may also be possible to maximize visual development and to limit any reduction in visual function," they said.

Many children with Down syndrome have significant refractive errors resulting in reduced visual acuity as measured with optotype testing. Optical correction of these refractive errors may not improve the visual acuity as well as expected. This article suggests that reduced visual acuity in children with Down syndrome is secondary to compromised cortical visual function as measured by diminished Vernier performance.

These findings may help to explain why we can’t always improve the visual acuity in patients with Down syndrome following refraction in otherwise healthy eyes.

– Rudolph S. Wagner, MD
OSN Pediatrics/Strabismus Board Member